The AIDS pandemic was a devastating global health catastrophe, reversing decades of progress in life expectancy and quality of life that had been made worldwide.

The pandemic was caused by the spread of HIV-1, a virus from chimpanzees that evolved into one that infects humans. Ever since, this global public health issue has posed major obstacles for global development and human security.

Origins

At the dawn of modern HIV science, little was understood about this deadly virus. How it spread and who would be most at risk were unknowns; fear of contracting the virus fuelled prejudice against at-risk populations like drug users and homosexuals alike.

Determining the origins of the AIDS pandemic proved challenging. While many theories exist, few consensus exists on a definitive cause.

The human immunodeficiency virus (HIV) is the cause of AIDS and it spreads through sexual contact. Additionally, blood transfusions or sharing contaminated medical equipment like needles and syringes can also spread the virus.

At present, there are two primary types of HIV: group A and group B. Both have evolved to infect human cells, but their duration in the body varies.

Group A HIV is the most widespread type, accounting for 80-90% of cases worldwide. It primarily exists in Africa, Asia and Latin America.

There are also subtypes of HIV that have spread beyond Europe and the United States, including subtypes B and C.

Subtypes of HIV have been derived largely from viruses found in apes and monkeys. These ape-adapted viruses, known as lentiviruses, have been detected in several species of African monkeys and apes (Fig.1).

Additionally, some close relatives of lentiviruses can be found in other primates, such as chimpanzees and gorillas. Collectively known as simian immunodeficiency viruses or SIVs, these lentiviruses have also been isolated from other mammals.

These simian lentiviruses are not pathogenic in their natural hosts, but can infect humans through the gut or bloodstream. It is believed to have been spread into humans either through contact with infected apes or through the bite of an infected ape.

In colonial west central Africa, around 1910 to 1930, the HIV virus made its initial appearance. Here were found to have emerged the four subtypes of HIV-1 that eventually lead to AIDS; further analysis has shown that all four subtypes emerged from a common ape-adapted precursor virus (Korber et al. 2000; Lemey et al. 2004; Worobey et al. 2008).

Symptoms

Aids is the result of immune system damage caused by HIV infection. It can be a devastating and life-threatening condition that typically progresses over years from mild infection into full blown AIDS.

HIV can cause flu-like symptoms that typically go away after one to four weeks of infection, but it also has the ability to hide in your body for extended periods without making you ill. Once established, HIV destroys CD4 cells (helper T cells), weakening your immunity against infections and some types of cancers.

At AIDS, your CD4 cells become so small that they cannot fight off infection or other disease. You may develop many infections which would usually be treatable in healthy people, such as hepatitis C and tuberculosis; additionally, certain cancers like lymphoma or Kaposi sarcoma on the skin could develop.

In the mid to late 1970s, doctors in Los Angeles and New York began to detect rare forms of pneumonia, cancer and other illnesses in men who had sexual contact. These conditions were known as opportunistic infections - not typically seen among people with healthy immune systems.

Years of research were needed to discover effective medications that could slow the progression of AIDS and prevent deaths caused by the illness. But in 1996, antiretroviral treatment (ART) became available for the first time.

To gain more knowledge about HIV and the symptoms experienced by those living with it, please visit our CDC website.

HIV infection causes AIDS, a long-term condition in which the human immunodeficiency virus (HIV) damages your immune system and makes it difficult to fight off infections and certain cancers. HIV weakens this defense system by destroying white blood cells - the building blocks of immunity - within it.

Common symptoms of HIV infection include fever, fatigue, weight loss, chronic weakness and night sweats. Other potentially life-threatening signs may include wasting syndrome which causes dehydration and severe weakness.

Treatment

HIV (human immunodeficiency virus) wreaks havoc on your immune system by destroying CD4 cells that protect you against infections and certain cancers. Left untreated, HIV can gradually weaken your defences until AIDS (acquired immunodeficiency syndrome) sets in.

Today, HIV can be effectively treated and managed through medications. Additionally, preventive measures like abstaining from sexual activity and using condoms are effective at preventing HIV infection in the first place.

The AIDS pandemic remains one of the world's greatest public health crises, but the rate of new HIV cases has significantly declined from its peak and appears to have plateaued recently. A global commitment exists to halt new infections and ensure everyone living with HIV receives access to appropriate treatment.

Accomplishing this goal requires an integrated strategy and coordinated action across the entire HIV response. This includes prevention, diagnosis and treatment as well as community-based support services.

Coordinating resources and partnerships at local, national, regional, and global levels will be necessary to end HIV/AIDS by 2030. Delivering appropriate care to people living with HIV and offering them necessary support will be key components in reaching this goal.

Treatment options for those living with HIV include pills and shots. Oral pre-exposure prophylaxis can also be utilized to protect those living with HIV from contracting the virus when exposed.

Antiretroviral therapy (ART) is the recommended treatment for all people living with HIV, regardless of their viral load or CD4 count. ART slows the progression of HIV to AIDS, reduces the risk of transmitting HIV, prevents opportunistic infections and keeps people healthy.

Antiretroviral therapy works by blocking HIV receptors that allow the virus to reproduce in the body, and can be combined with other treatments to address other conditions that may arise among those living with HIV.

In some countries, treatment has reduced HIV death rates by up to 75%. Unfortunately, much of the burden remains in Sub-Saharan Africa where life expectancies have only recently returned to pre-epidemic levels.

Prevention

HIV (human immunodeficiency virus) causes AIDS, a serious illness caused by its human immunodeficiency virus. Without treatment, people living with HIV may develop a weak immune system that makes it difficult for their bodies to fight off infections or certain types of cancer. With antiretroviral therapy however, people living with HIV typically live normal or near-normal lives while decreasing the chance of dying from AIDS.

Despite recent progress, HIV and AIDS remain major public health threats. Worldwide, approximately 38 million people live with HIV, while more than 10 million succumb to AIDS-related causes each year.

People living with HIV may be more vulnerable to opportunistic diseases like tuberculosis (TB) or hepatitis C than they were before the AIDS pandemic began. Though these illnesses can lead to severe illness or even death in some cases, these conditions are much less frequent among those treated with antiretroviral therapy compared to before the epidemic started.

Preventing HIV and AIDS requires a multifaceted approach. These include preventing new infections with condoms, medical circumcision and syringe access; HIV testing and linking to care; as well as interventions that quickly treat and suppress HIV in those who test positive or have already been diagnosed.

Preexposure prophylaxis (PrEP) is a widely-used strategy to protect those at high risk of contracting HIV. This involves taking daily oral antiretroviral drugs like efavirenz and nevirapine as well as injectable options like lamivudine or raltegravir.

PrEP is especially essential for individuals who are more at risk of contracting HIV, such as cisgender men and transgender people who have sexual activity with men; young adults and adolescents; people from regions with high HIV incidence rates; those with hepatitis C; and those who inject nonprescription drugs like opioids or methamphetamine.

Prevention experts agree that the most successful prevention strategies involve altering social, political and economic conditions so perpetration is less likely. These efforts are referred to as either "primary" or "secondary" prevention initiatives.

Thirdly, tertiary prevention works to enhance quality of life by avoiding or decreasing negative health outcomes and creating conditions for people to thrive. For instance, primary prevention efforts can reduce teen pregnancy by changing laws and norms around sexual behavior; secondary and tertiary prevention measures ensure pregnant women receive appropriate prenatal care.